2006 Altima 2.5 Project

I've been interested in upgrading the stock internals. It's an automatic. I get a lot of shit when I mention I want to upgrade an automatic, but it's something I've wanted to do for a while now. What would you recommend I do? I stay in CA. I have no idea where to start. Should I buy upgraded internals for the QR25 and do it myself or take it somewhere like 2J Racing. Can I somehow upgrade the stock auto tranny to handle a turbo? What are good turbos for this car? How do I go about tuning the car if all this is done? It's just some little dream of mine to fix this car up and would greatly appreciate any info.